Process for manufacturing detergent tablet



United States Patent 3,231,505 PRQCESS lFGR MANWACTURING DETERGENT TABLET Richard Edward Farrar, Morris Plains, and Joseph L. Sweeney, Kearny, Ni, assignors to Colgate-Palmolive Company, New York, Nfifl, a corporation of Delaware No Drawing. Filed Apr. 3, 1961, Ser. No. 100,032 5 Claims. (ill. 252-438) The present invention relates to a detergent tablet which is resistant to abrasion and accidental breakage when dry and is also adequately disintegrable in water in normal laundering operations. The invention includes a process for manufacturing such a briquetted tablet by coating detergent particles with soluble silicate compounds, lightly compacting the coated particles to a form-retaining briquette and applying to the surface of the briquette a coating of readily water soluble film-forming organic polymer.

It has been discovered that the production of detergent tablets from particulate detergent compositions comprising nonionic detergents can be facilitated and the products can be improved by following the herein described processes.

In accordance with this invention, a process for manufacturing a briquetted detergent tablet begins with mixing together water soluble solid inorganic salt and water soluble nonionic organic detergent and producing therefrom a particulate detergent containing up to 21% moisture. To the particles is applied an aqueous solution of soluble silicate, preferably by spraying. Three to 20% of the soluble silicate coats the particles and increases the moisture conent to about 16 to 25%. Next, to the coated detergent particles may be added 0.5 to 5% of finely divided water insoluble inorganic silicate to form another coating, held to the particles by the water soluble silicate. The coating with insoluble silicate is not essential but does measurably improve the ease of pressing the detergent particles into tableted form and allows high speed production on a commercial scale. After coating with insoluble silicate, if it is employed, the detergent particles are pressed into a solid form-retaining briquetted tablet at a pressure low enough to form a tablet which is readily disintegrable in water, after which about 0.25 to 5% of a readily water soluble synthetic film-forming organic polymer is applied to the tablet to form on the surface thereof a water soluble film which is of sufficient strength to help make the detergent tablet resistant to abrasion and accidental breakage, when dry, and of a solubility such that the detergent tablet is readily disintegrable in water.

In following the invented process, it is preferred to mix together the major constituents of a heavy duty synthetic organic detergent composition, including nonionic detergent and inorganic builder salts, in an aqueous solution or dispersion, usually containing 2070% solids. The uniform slurry is atomized and sprayed into a heated dryinggas to form a spray dried detergent in particulate form, preferably of a low-suds'ing type formula. Instead of spray drying, other production techniques may be employed to produce such detergent powders.

The dry or partially dried detergent is agitated, as by tumbling in a rotating inclined drum, and while being so moved, is sprayed with a solution of water soluble silicate. The silicate is spread over the surfaces of the particles by the tumbling action and causes the finer particles present to adhere to others to form particles of larger size. This agglomeration is often accompanied by a decrease in density. In addition to altering product density, the silicate conditions the particles so that they will adhere together better in subsequentbriquetting operations.

After coating with silicate and continuing mixing for about one to five minutes, a finely divided water insoluble silicate powder, preferably tale that will pass a 260 mesh sieve, may be distributed over the particles previously 3,231,505 Patented Jan. 25, 1966 coated with soluble silicate. The tale coating helps to arrest agglomeration and improves ease of briquetting. The tale is preferably applied in the same mixing drum as the slicate, preferably as a fluidized powder blown into the mixer by air pressure. After about 5 to 15 minutes mixing the treated detergent particles are withdrawn, oversized agglomerates are screened out and the product,.preferably as agglomerates of particle size within therangeof 6 to 60 mesh, is removed. The coatingprocess described above may be either of the batch type or continuous, the latter being preferred for high speed commercial-procedures.

The coated detergent maybe immediately pressed into briquetted tablet form or may be "temporarily stored for several hours before compacting. The-free flowingparticles are fed to 'mold cavities and are lightly compacted to desired shape, at a pressure of about 10 to lOfl'pounds per square inch, preferably about 40-to pounds ,per square inch. The pressure employed is that at which the tablets are made resistant to abrasion and' accidental breakage, when dry, and are still readily disintegrable in water. Thus, in a simulated washing machine'test, freshly made tablets, also coated 'with organic polymer as discussed below, should disintegrate in agitated water-at room temperature in less than'90 seconds, preferably less than 60 seconds. When aged, the hardened tablets may take as long as 4 minutes to break up completely. Although" it is desirable to have the most rapid solubility characteristics possible, even the aged tablets still dissolve fast enough in usual laundry usage to wash satisfactorily.

The lightly compacted tablets are next sprayed with a protective coating of an organic film forming polymer, preferably polyvinyl alcohol, usually as an aqueous solution applied in spray form. The 'entire'briquet'te surface is covered and a strong bond between the polyvinyl'alcohol and the previous soluble silicate coating is obtained. To speed production and make a hard'protective coating on the detergent tablet, the polyvinyl alcoholcoating is dried by infra-red heating lamps. The finished tablets are then packed in'plastic bags or sleeves, boxed, cased and shipped.

The products made according to the invention are strong and withstand rigid shipping and handling tests without occurrence of objectionable breakage. Yet,"'t-l1e tablets disintegrate readily in water.

The materials of the present compositions'andtheprocessing operations will now be described in greater detail to enable one of skill in this art better to appreciate the significance of the invention.

The water soluble nonionic organic detergent is'prefi erably an alkyl phenoxy poly lower alkoxy alkanol and nonyl phenoxy polyoxyethylene ethanoloif about 9 to 10 ethoxy groups is a specificexanrple of this group found to be excellent. In the preferred class of compounds mentioned the alkyl group is usually of 6 to 14 carbon atoms and the alkoxy chain is of 4 i012 units long, each unit comprising from two to four'carbon atoms. Commercial products of this type are usually mixtures and mixes of this and other types of water soluble non-ionic detergents may be employed. Thus, in appropriate formulas, other nonionics, such as theblock'copolymers of ethylene oxide and propylene oxide (Pluronics),'reaction products of higher fatty alcohols and lower alkylene oxide (Enrulphogene), polyoxyethylatedhighe'r fatty acids (Emulphor), polyethoxy and poly lower alkoxy esters and ethers of sugar alcohols, especially of sorbitol and mannitol (Span, Tween), may be used in addition to the alkyl phenoxy polyoxyalkylene alkanol and in some cases in replacement thereof. In the present detergent compositions the proportion of nonionic-detergentyon a final product weight basis, as are all other proportions given, is usually 4 to 14%, preferably 7 to 12%.

' quette.

In addition to nonionic detergent, an anionic detergent may also be present, usually primarily to produce some foam and to contribute its cleaning power to the composition. A preferred detergent of this type is sodium tridecyl benzene sulfonate, a mixture of detergents, the alkyl groups of which are derived from a mixture of propylene tetramer and pentamer. The alkyl groups may be of other structures of to 18 carbon atoms and these compounds may be used as their other water soluble metal salts of similar properties. In place of some or all of the alkyl benzene sulfonate, one may employ other anionic sulfated or sulfonated organic detergent compounds containing fatty alkyl or acyl groups of 10-18 carbon atoms, such as sodium lauryl sulfate, sodium coconut oil fatty acids monoglyoeride sulfate and a sodium salt of a higher fatty acid amide of N-methyl taurine. The proportion of anionic detergent should normally be from about 1 to 5%.

A foam stabilizer, such as a long chain fatty compound having an alkyl group of 12 to 18 carbon atoms, preferably a mixture of cetyl and stearyl alcohols, may also be included to thicken the foam produced by the anionic detergent. Ordinarily, 0.5 to 5% and preferably 0.5 .to 3% of this material is enough.

The inorganic water soluble normally solid salt is preferably a builder salt'of the polyphosphate type, such as pentasodium tripolyphosphate. Other useful builders and fillers include alkali metal sulfates, sodium and potassium carbonates, tetrasodium pyrophosphate and sodium silicates of various Na O/SiO ratios. These give the present tablets a useful and functional base for the organic materials. From 30 to 75% of the product may be soluble inorganic salt and preferably 30 to 50% sodium tripolyphosphate is used in mixture with smaller proportions of sodium silicate (Na O/SiO ratio of 1:235) and sodium sulfate.

Following the spray drying method mentioned earlier, a slurry of the above materials in an aqueous medium is dried to a moisture content of 7 to 14%. By this and other methods, moistures of up to 21%, usually 2 to 18%, are obtainable and particles of such moisture contents can be made into satisfactory tablets by the present methods. If the spray dried particles are high in fines or coarse pieces, they should be screened or classified to substantially all (90% or more) held by a 100 mesh sieve (U.S. Standard Series) with none on 6 or 8 mesh The silicate solution sprayed onto the detergent beads when they are being tumbled or otherwise agitated is a water soluble metal silicate. Of the alkali metal silicates, the best is a sodium silicate of an Na O/SiO ratio from 1:2 to 1:3, most preferably 122.35. This silicate is made into an aqueous solution which may be 'of 25 to 46% solids content. Generally the silicate solution will be of 35 to 43.5% solids content,preferably about 35 to 37%. The selected concentrations given can be satisfactorily stored and sprayed. The proportion of water solution of sodium silicate sprayed onto the moving detergent bead surfaces is usually 15 to 30%, preferably about Thus, 15 to 30 parts solution are sprayed onto about 85 to 70 parts of detergent beads, neglecting a minor cor rection to compensate for the small amounts of coating applied later. The 3 to 15% silicate solids coating added, preferabily 6.5 to 8.5% helps to agglomerate thebeads to a 6 to 60 mesh particle .size range (about 0.25 to 4 millimeters diameter) and helps to create a strong bri- It also raises moisture content to 16 to 17 to 24% and preferably 17.5 to 20.5%, the best concentrations for the briquetting operations.

After coating with the silicate and continued mixing and agglomerating, the tumbling beads may next be coated, if desired, with a very finely divided talc. Other magnesium silicates or other finely divided water insoluble inorganic silicates, such as cfeldspars, micas, etc., of equivalent properties may be used with or in place of talc. 0.5 to 5% talc is sufficient to hinder further agglomeration and improves the speed and ease of pressing. After the particles are coated with talc, they are removed from the tumbling zone and are immediately ready for pressing into tablets.

In pressing, the detergent particles are flowed into molds or pockets in high speed shaping equipment. Opposed dies of Teflon in a Teflon-lined sleeve or die-box compact the particles into flat, circular tablet form, beveled and with a diametric score line to facilitate breaking in half, if desired. The dies are set with stops to make tablets of constant thickness, so the same volumes of detergent are charged accurate-1y so that compacting pressures may be kept within the correct range of 10 to 100 pounds per square inch. After compacting and easy removal [from dies, the pressed tablets, due to their silicate coatings, can be handled Without fear of objectionable breakage. However, such tablets would not be permanently satisfactory unless subsequently coated with a water soluble polymeric film-forming compound, such as polyvinyl alcohol.

The polyvinyl alcohols of commerce usually contain minor proportions of a lower fatty acid ester, polyvinyl acetate. This may be present in polyvinyl alcohols employed in carrying out'the processes of this invention to the extent of about 10 to 30%. The useful polyvinyl al cohols are also of a weight degree of polymeriaztion between about 30 and 300. A good polyvinyl alcohol for use in accordance With this invention has a weight average degree of polymerization of about 50 to 250 (viscosity of about 2 to 6 centipoises) and a polyvinyl acetate content of 15 to 25% and a most preferred material has a weight average degree of polymerization of about 100 (viscosity of 3.5 centipoises) and polyvinyl alcohol content of with 20% polyvinyl acetate.

The polyvinyl alcohol should contain relatively little insoluble matter, should be colorless, odor-free and of neutral pH. Deviations from the above requirements may be made where warranted but, in general, the polyvinyl alcohol of the recited specifications would be most acceptable for household detergent products. Instead of the described polyvinyl alcohol, other readily water soluble synthetic organic film-forming polymers of similarly useful properties can be used, but usually such compounds will not be as effective. However, polyvinylpyrollidone, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose and similar polymeric substances can produce water soluble films or coatings for briquette surfaces. When used, it is preferred to mix them with polyvinyl alcohol so that the special advantages attending the presence of that material may be retained.

Coating of the detergent tablet is preferably done by spraying onto the surfaces a liquid comprising the polyvinyl alcohol dissolved in water. The aqueous solution should be sprayed or atomized in fine droplet form as evenly as possible onto the surface of the tablet. The spray solution may contain glycerol or other lower polyols to serve as plasticizers to help to keep the polyvinyl alcohol flexible and resilient, detergents or wetting agents to improve the wetting of the briquetted tablets and nuetralizing agents, e.g., sodium bicarbonate, to improve the odor of the polyvinyl alcohol by reacting with free acid that might be present. Among other plasticizers that find use are glycols, e.g., ethylene glycol and sugar alcohols, such as sorbitol.

The amount of polyvinyl alcohol sprayed onto the tablet surface should be from 0.25 to 5% of the briquette weight, preferably 0.3 to 1%. The polyvinyl alcohol is preferably applied as a 10 to 25 solution, such as a 17% solution in Water, the proportion of such solutions being used. being from 3 to 10%, preferably about 6% of the tablet weight. When sprayed onto the detergent briquette surface, the polyvinyl alcohol and its solvent fill the voids between the particles and also cover the surfaces of the particles. Because the briquette before coating is not perfectly smooth, it is evident that the coating will be thicker in some spots than in others but it may be said that the average thickness will be approximately from 0.01 to 0.8 millimeter, preferably 0.02 to 0.1 millimeter.

After coating with polyvinyl alcohol solution, the tablet may be surface dried by forced air, heated air, infra-red rays or other suitable drying means to remove essentially all the solvent accompanying the polyvinyl alcohol in the coating spray. Thus, the final product will be of about the same moisture content as that obtaining in the particles before pressing. After drying, the tablets may be packed immediately into cartons ready for shipment and use. It is usually preferred to have moisture barriers in such cartons to assist in maintaining the correct moisture content in the briquette during what may be an extended storage period. Briquettes made in accordance with this invention may be shipped commercially without breaking and even though stored for months before use will still disintegrate and dissolve rapidly enough when added to the tub of any of the conventional Washing machines. They will also pass severe strength and solubility tests set for such products, withstanding a drop of at least one foot onto a hard surface, e.g., a metal plate, without breaking and also disintegrating in agitated water at 100 Fahrenheit in a washing machine within a period of no greater than 4 minutes, usually within one minute. The washing machine referred to is a commercial top-loading machine with a center post agitator of average operating and design characteristics.

The following examples illustrate the invention. All percentages and proportions in the examples, this specification and the appended claims are by weight unless otherwise indicated.

Example I Higher alkyl phenoxy polyethoxy ethanol (alkyl group of about 9 carbon atoms and ethoxy chain of'9 to 10 units) Sodium higher alkyl benzene sulfonate (alizyl group This formula was obtained by spray drying of an aqueous slurry by atomization into heated drying gas, according to normal spray tower procedures. The spray dried detergent obtained was screened and was substantially all, over 90% within the 8 to 100 mesh US. Standard Sieve Series range. Particles outside this range were substantially all less than 100 mesh in size.

The spray dried beads were fed to a tumbling zone,

where they were agitated in such manner that a curtain or thin falling stream of particles was sprayed with droplets of silicate solution. The silicate employed Was of Na O/SiO ratio of 0.43 or 1:2.35, silicates of Na O/SiO ratios greater than 1:2 and less than 1:3 being less satisfactory. The detergent beads Were sprayed with and 27% of a 43.5% solution of soluble sodium silicate. The concentration of silicate used may be varied from to 46% and still the treated beads obtained will be satisfactory. However, when the lower concentrations are employed, as when bead moisture is initially low, it is usually desirable to increase the amount of solution applied to assure that enough silicate is on the bead surfaces.

After spraying with silicate the detergent particles are tumbled for about 15 minutes so that the silicate will be evenly distributed. During tumbling some finer particles are agglomerated, product density is decreased and particle size is raised to 6 to 60 mesh.

The silicate coated beads, their moisture content raised to about 15%, 20% and 24% respectively, are immediately compacted at a pressure of about pounds per square inch, to form a shape-retaining briquette, held together by the silicate coating to a substantial extent but not so tightly compacted as to objectionably resist disintegration in water under washing conditions. The briquettes made are sprayed with polyvinyl alcohol of weight average molecular weight of about and polyvinyl acetate content of about 20%. 0.8 to 1% of the technical polyvinyl alcohol is applied evenly to the briquette by spraying, as an aqueous solution and the coating, anirregular film of an area of about 15 square inches is heat dried to hardness.

In place of the alkyl benzene sulfonate in this formula one may use other anionic detergents such as sodium lauryl sulfate or higher fatty acid amide of N-methyl taur-ine. The nonionic detergent may be partially replaced by other nonionics such as the block 'copolymers of ethylene'oxide and propylene oxide (Pluronic F-68) and polyethoxy esters of higher fatty acids and alcohols. Also the fatty alcohol may sometimes be replaced with fatty acids of about the same chain length.

The finished tables are attractive, non-dusting and sufficiently strong to be handled in commerce without breakage. Of course, they should be packed so that there is no excessive shaking or rattling in shipment. Also, .a moisture barrier packing will keep the tablets from drying out to a more brittle state. These tablets can withstand drop tests and simulated shipping tests. Even though they are so strong, the tablets still disintegrate rapidly in water in a washing machine. No undissolved lumps are found in clothing, even after washing with warm of cool water. Usually freshly made briquettes dissolve within about 60 seconds in water at 100 F. agitated to simulate normal washing motions.

Example ll Nonyl phenol ethoxylate (9.5 ethylene oxides) 13 Sodium tridecyl benzene sulfonate 5 Technical cetyl alcohol 1 Sodium tripoly-phosphate 43 Sodium sulfate 25 Sodium silicate (N a O/SiO ratio of 112.35 4 Moisture 8.5

Adjuvants (anti-redeposition agent,

fluorescent brightener, perfume, anti-oxidant 0.5

The above formula was made by spray drying an aqueous crutcher mix slurry of all materials except perfume which was added after spraying. In a tumbling drumthere were added to 100X parts of spray dried particles of such formula of size from 8 to 100 mesh by spraying the following amounts and concentrations of a water solution of sodium silicate of Na O/SiO ratio of 1:2.35. Moisture contents of briquetted tablets made therefrom are also given.

(X) Parts silicate solution Percentage Final Solids Moisture After about 5 minutes tumbling, talc powder, substant-ally all less than 200 mesh, was air-blown onmo the tumbling particles. The amount of talc used was 2% and the beads were agitated. for another ten minutes, after which they had been agglomerated to 6 to 60' mesh and were ready for immediate pressing. (The addition of talc is not essential and in comparable experiments satisfactory products have been obtained by practicable methods like that of this example without talc or other insoluble silicate. However, work subsequent to the present invention disclosed talc to be useful and desirable and therefore it is shown in this example.) Within a period not greater than two hours, the coated particles were pressed to flat cylinder shape at a pressure within the 40 to 90 pounds per square inch range and spray coated with about 0.8%

polyvinyl alcohol in a 17% aqueous solution at about 150 F. The polyvinyl alcohol was of Weight average degree of polymerization of about 100 and contained 15-25% polyvinyl acetate. After coating of the tablet the polyvinyl alcohol was dried under infra-red lamps. The coating made was of irregular thickness, between 0.01 and 0.8 millimeter.

The tabllet resulting pressed very easily into the automatic machinery employed (having Teflon dies and sleeves) and satisfactorily passed drop tests, shipping tests and disintegration tests (in water). They are attractive in appearance, dust free and easy to use. The polyvinyl alcohol of the coating even increases the anti-redeposition properties of the detergent. In storage the tablets did not swell or crumble, but retained their original shapes and surface appearances. The could be shipped, even in cold weather, and when packed properly, exhibit a surprisingly good resistance to breakage.

The present invention has been illustrated by description of the invented products made and manufacturing methods employed. These examples are illustrative only and are not to be considered as limiting the allowed claims.

What is claimed is:

1. A process for manufacturing a briquetted detergent tablet comprising mixing together about 4 to 14% of a water soluble nonionic organic polyethoxy detergent seilected from the group consisting of ethoxylated alkyl phenol, ethoxylated higher fatty alcohol, ethoxylated higher fatty acid and ethoxylated propylene oxide polymers with about 30 to 75% of a normally solid water soluble inorganic alkali metal builder salt, producing therefrom a particulate detergent containing up to 21% moisture, applying an aqueous solution of soluble alkali metal silicate to the particulate detergent to coat the particles with 3 to 20% soluble alkali metal silicate to cause agglomeration into larger particles, substantially all within the size range of 6 to 60 mesh, and to increase the moisture content thereof to about 16 to 25%, pressing the detergent particles into a solid form-retaining briquetted tablet at a pressure of about 10 to 100 pounds per square inch to form a tablet which is readily disintegrable in water and applying to the tablet about .25 to of a readily water soluble synthetic organic film-forming polymer selected from the group consisting of polyvinyl alcohol, polyvinylpyrollidone, sodium carboxymethylcellulose and hydroxypropyl methyl cellulose, to form on the briquette surface a water soluble film which is of strength sufficient to help make the detergent tablet resistant to abrasion and accidental breakage, when dry, and of solubility such that the detergent tablet is readily disintegrable in water.

2. A process for manufacturing a br-iquetted detergent tablet which is resistant to abrasion and accidental breakage, when dry, and readily disintegrable in water, comprising mixing together 4 to 14% of a water soluble nonionic synthetic organic detergent which is an alkyl phenoxy polyoxyethylene ethanol having 6 to 14 carbon atoms in the alkyl group and 4 to 12 ethylene oxide units, 1 to 5% of a water soluble metal salt of higher alkyl benzene sulfonic acid in which the alkyl group is of to 18 carbon atoms, 0.5 to 5% of a foam stabilizer which is a long chain fatty alcohol having an alkyl group of 12 to 18 carbon atoms, and 30 to of a water soluble inorganic alkali metal builder salt, producing therefrom a particulate detergent containing 2 to 18% moisture, applying 15 to 30% of an aqueous solution of 25 to 46% solids content sodium silicate of Na O/SiO ratio of 1:2 to 1:3 to the particulate detergent to coat the particles with 3 to 15% sodium silicate to cause agglomeration into larger particles, substantially all within the size range of 6 to 60 mesh, and to increase the moisture content thereof to about 17 to 24%, pressing the detergent particles into a solid form-retaining briquetted tablet at a pressure of 10 to 100 pounds per square inch, low enough to form a tablet which is readily disintegrable in water, and applying to the tablet about .25 to 5% of a readily water soluble polyvinyl alcohol.

3. A process for manufacturing a briquetted detergent tablet which is resistant to abrasion and accidental breakage, when dry, and readily disintegrable in water, comprising mixing together an aqueous slurry of 7 to 12% of a water soluble nonionic synthetic organic detergent which is nonyl phenoxy polyoxyethylene ethanol of about 9 to 10 ethoxy groups, 1.5 to 5% of sodium alkyl benzene sulfonate in which the alkyl group is of 12 to 15 carbons atoms, 0.5 to 3% of fatty alcohol foam stabilizer having a fatty alkly group of 12 to 18 carbon atoms and 30 to 50% of sodium tripolyphosphate builder salt, spray drying the slurry to form particles of moisture content of 7 to 14% and of particle size substantially all between 6 and 100 mesh, tumbling the partially dried particles and while tumbling, spraying onto the particles 15 to 30% of an aqueous solution of 35 to 43.5% solids content sodium silicate of Na O/SiO ratio of about 1:2.35 to coat the particles with 6.5 to 8.5% sodium silicate, to increase the moisture content thereof to 17.5 to 20.5% and to cause agglomeration into larger particles, substantially all within the size range of 6 to 60 mesh, pressing the detergent particles into a solid form-retaining tablet at a pressure of 40 to pounds per square inch, low enough to form a tablet which is readily disintegrable in water, spraying the tablet with. 0.3 to 1.0% readily water soluble polyvinyl alcohol, in aqueous solution, the polyvinyl alcohol being of a weight average degree of polymerization of about 30 to 300 and a polyvinyl acetate content of about 10 to 30% thereof, and drying the polyvinyl alcohol solution to form a water soluble protective film coating.

4. A water soluble detergent briquette which is resistant to abrasion and accidental breakage, when dry, and disintegrates readily in water, comprising a multiplicity of solid particles composed of a homogeneous mixture of about 4 to 14% of a water soluble nonionic organic polyethoxy detergent selected from the group consisting of ethoxylated alkyl phenol, ethoxylated higher fatty alcohol, ethoxylated higher fatty acid and ethoxylaited propylene oxide polymers and about 30 to 75% of a water soluble inorganic alkali metal builder salt, and 16 to 25% moisture content, in the form of adhering particles initially of moisture content up to 21%, coated with 3 to 20% water soluble alkali metal silicate, the coated particles substantially all within the size range of 6 to 60 mesh being lightly compacted at a pressure of about 10 to pounds per square inch to forma shaped briquette, which is coated with an adhering and binding film of 0.25 to 5% of a readily water soluble polyvinyl alcohol of a weight average degree 'of polymerization of about 30 to 300 and a polyvinyl acetate content of about 10 to 30% which forms on the surface of the detergent briquette a water soluble coating of an average thickness from about 0.01 to 0.8 millimeter.

5. A water soluble detergent briquette which is resistant to abrasion and accidental breakage, when dry, and disintegrates and dissolves readily in water, comprising a multiplicity of agglomerated spray dried solid particles of diameters substantially within the range of 0.25 millimeter to 4 millimeters, composed of homogeneous particles comprising a mixture of 7 to 12% of nonyl phenoxy polyoxyethylene ethanol of about 9 to 10 ethoxy groups, 1.5 to 5% of sodium alkyl benzene sulfonate detergent in which the alkyl group is of 12 to 15 carbon atoms, 0.5 to 3% of fatty alcohol of 12 to 18 carbon atoms and to of sodium tripolyphosphate coated with 6.5 to 8.5% of sodium silicate of Na O to Si0 ratio of about 1:2.35 the coated particles being in the form of adhering particles of moisture content of 17.5 to 20.5%, lightly compacted at a pressure of about 10 to pounds per square inch, the compacted tablet being coated With an aidfliering and strengthening binding film of 0.3 to 1.0% of a readily soluble polyvinyl alcohol of a Weight average degree of polymerization of about 100 and a polyvinyl acetate content of 15 to 25% which for-ms on the surface of substantially the whole detergent btiquette a Water soluble coating of thickness averaging about 0.02 to 0.1 millimeter.

References Cited by the Examiner UNITED STATES PATENTS 2,382,165 8/1945 MacMahon 257- XR 2,636,008 4/1953 Jurgensen et a1. 252-93 2,855,367 10/1958 Buck 252138 2,875,155 2/1959 Miles 252-138 FOREIGN PATENTS 141,503 6/1951 Australia.

OTHER REFERENCES Merril, Industrial Applications of the Sodium Silicates, Ind. and Eng. Chem., vol. 41, No. 2 (February 1949), pp. 377-345.

Elvanol, Polyvinyl Alcohols, E. I. du Pont de Nemoui's & Co., Inc., Copyright 1947.

JULIUS GREENWALD, Primary Examiner. 

1. A PROCESS FOR MANUFACTURING A BRIQUETTED DETERGENT TABLET COMPRISING MIXING TOGETHER ABOUT 4 TO 14% OF A WATER SOLUBLE NONIONIC ORGANIC POLYETHOXY DETERGENT SELECTED FROM THE GROUP CONSISTING OF ETHOXYLATED ALKYL PHENOL, ETHOXYLATED HIGHER FATTY ALCOHOL, ETHOXYLATED HIGHER FATTY ACID AND ETHOXYLATED PROPYLENE OXIDIC POLYMERS WITH ABOUT 30 TO 75% OF A NORMALLY SOSLID WATER SOLUBLE INORGANIC ALKALI METAL BUILDER SALT, PRODUCING THEREFROM A PARTICULATE DETERGENT CONTAINING UP TO 21% MOISTURE, APPLYING AN AQUEOUS SOLUTION OF SOLUBLE ALKALI METAL SILICATE TO THE PARTICULATE DETERGENT TO COAT THE PARTICLES WITH 3 TO 20% SOLUBLE ALKALI METAL SILICATE TO CUASE AGGLOMERATION INTO LARGER PARTICLES, SUBSTANTIALLY ALL WITHIN THE SIZE RANGE OF 6 TO 60 MESH, AND TO INCREASE THE MOISTURE CONTENT THEREOF TO ABOUT 16 TO 25%, PRESSING THE DETERGENT PARTICLES INTO A SOLID FORM-RETAINING BRIQUETTED TABLET AT A PRESSURE OF ABOUT 10 TO 100 POUNDS PER SQUARE INCH TO FORM A TABLET WHICH IS READILY DISINTERGRABLE IN WATER AND APPLYING TO THE TABLET ABOUT .25 TO 5% OF A READILY WATER SOLUBLE SYNTHETIC ORGANIC FILM-FORMING POLYMER SELECTED FROM THE GROUP CONSISTING OF POLYVINYL ALCOHOL, POLYVINYLPYROLIDONE, SODIUM CARBOXYMETHYLCELLULOSE AND HYDROXYPROPYL METHYL CELLUSLOSE, TO FORM ON THE BRIQUETTE SURFACE A WATER SOLUBLE FILM WHICH IS A STRENGTH SUFFICIENT TO HELP MAKE THE DETERGENT TABLET RESISTANT TO ABRASION AND ACCIDENTAL BREAKAGE, WHEN DRY, AND OF SOLUBILITY SUCH THAT THE DETERGENT TABLET IS READILY DISINTEGRABLE IN WATER. 